An increase in the incidence of infections caused by various fungi, e.g., yeasts, and yeast like algae in recent years has emphasized the need for a rapid means of their identification. In a compromised individual a yeast infection often proves rapidly fatal. Thus, providing the physician with an accurate, same-day (rapid) identification can influence a more effective treatment for the infected patient.
Fungi are ubiquitous, eucaryotic microorganisms and differ in many ways from bacteria. Yeasts for example, grow more slowly than bacteria--a mature culture requires 48-72 hours incubation in contrast to 18-24 hours for most bacteria.
Current identification procedures for fungi and yeast like organisms also require more time for incubation (with test substrates) than those used for bacteria. Thus, the two most frequently used commercial systems for identification of yeasts require incubation times after primary plate isolation of 3 and 6 days. Most commercial systems are modifications of either or both of two conventional techniques: Auxanographic or Wickerham procedures. The Wickerham procedure represents the classical, traditional approach to yeast taxonomy, but due to the tedious nature of this method (i.e., extensive media preparation, pipetting into multiple racks of test tubes and incubation for up to 6 weeks) mycologists have widely accepted more rapid modifications affording a high degree of reliability. The more rapid conventionally accepted method is Auxanography which examines the patterns produced by various carbohydrates supporting growth in the presence of a growth medium. Both the Wickerham and auxanographic methods utilize carbohydrates by assimilation in the presence of what is commonly known as Wickerham's yeast nitrogen base.
Carbohydrate fermentation tests have also been employed for the detection of yeasts. However these tests are more subject to variation than assimilations and are only considered reliable for yeasts when the fermentation process produces detectable gas. As with the assimilations, carbohydrate fermentation tests for yeasts rely on the further employment of a basal (growth) medium.
While both assimilation and fermentation carbohydrate tests have in isolated cases been rapidized to some degree, the most reliable identifications are attained only through longer incubation periods with the test substrates--for days or weeks.
More recently, the API ZYM System (Analytab Products, Plainview, New York) a system designed for the detection of enzyme activities with certain chromogenic substrates has been assessed as a means for generating enzymatic profiles which might be useful for the rapid identification of medically significant yeasts. (Bobey et al. ASM Ann'l. Mtg. 1980, Poster #C-254). The authors of that study considered that the ZYM system had the potential to distinguish between various yeasts, but too few isolates had been examined to determine whether characteristic patterns would emerge enabling identification.
Bobey and Ederer also investigated the use of fluorogenic substrates to access their usefulness in the rapid identification of medically significant yeast isolates (J. Clin. Micro., Feb., 1981, p. 393-394, Vol. 13, No. 2).
Currently there is no available system which applies or is capable of applying the technology of chromogenic substrates to the identification of yeasts and yeast like organisms.
Collection, transport and isolation of specimens relating to fungi are further explained, for example, in Chapters 52 and 55 of the 3rd Edition of the Manual of Clinical Microbiology (1980), both said chapters are herein expressly incorporated by reference. Another reference may be found in The Yeasts, 1970, 2nd Edition by J. Lodder.